The present invention relates to a process for the production of stable dispersions of polyureas and/or polyhydrazodicarbonamides in a hydroxyl-group-containing material.
Dispersions of polyureas and/or polyhydrazodicarbonamides in organic compounds containing hydroxyl groups are known and are used extensively in the polyurethane products. See, e.g., U.S. Pat. Nos. 3,325,421, 4,092,275, 4,093,569, 4,119,613, 4,147,680, 4,184,990, 4,293,470, 4,296,213, 4,305,857, 4,305,858, 4,310,448, 4,310,449, 4,324,716, 4,374,209, 4,496,678, and 4,523,025. In the commercial production of such dispersions, any water present is generally reduced to a level below 0.5% by weight. Before removal of the water, such dispersions typically contain around 1.5% by weight of water. For many applications, such as the manufacture of polyurethane shoe soles, the water content must be as low as possible. For other applications, higher water contents are desirable. However, when water is added to the dispersions after their formation, the viscosity of the resultant product may increase with time. In some instances, the increase can be quite dramatic.
One solution to the above-noted problem can be found in U.S. Pat. No. 4,496,678. The present invention is directed to yet another solution to the problem. Dispersions of this type have a relatively stable viscosity with time even when additional water is present.